The present invention relates generally to communication networks and more specifically to an intra-train communication network.
Intra-train communication using radio frequency signals allows each locomotive in a train to establish bidirectional data exchange. The locomotives may be at one end of the train in a consist or spread throughout the train. One challenge, in such an arrangement, is discerning locomotives in one train from those in another in order to distinguish data from each train. As the trains move across particular territories or terrains and are exposed to various levels of interferences, communication can be lost and must be re-established.
The present invention is an intra-train communication network including plurality of transceiver units on individual vehicles of a train. One of the transceiver units is a master unit transmitting queries or data request and the other units are slave units receiving the queries and transmitting responses. The master unit initially transmits queries which include a first ID from a first group of IDs to the slave unit using a second ID from a second set of IDs. Subsequently, the master unit transmits queries using the first ID from the first group.
The slave unit initially listens for queries using the second ID from the second group and responds using the second ID and then switches to the first ID from the first group in the query. Subsequently, the slave units listen for and respond using the first ID from the first group. A slave unit switches to listening for an available ID in the second group if the slave unit has not received a query within a first period of time. If the slave has not received a query from the master, it will alternate listening for the ID from the second group and for the ID from the first group.
The slave unit determines an available ID in the second unit as an ID in the second group which is in use no longer than a second period of time. The master unit determines the first ID for the first group as an ID in the first group which is not in use during a third period of time.
The master unit transmits to all slave units queries including the first ID and using the IDs of the second group if the master unit does not receive a response from any of the slave units in a fourth time period. Also, the master unit transmits to all slave units queries including the first ID and using the ID in the second group if the master unit does not receive a response from at least one of the slave units in the fourth time period and the speed of the train is zero. The master unit includes a list of all units in the network and only processes a response received from a unit in the list.
The master unit changes to a slave unit if the lead unit has requested to change from a master unit for a fifth period of time or the lead unit requests a change from a master unit and a slave unit has communicated over the network requested to become a master unit. During initialization all units are set to be slave units with an ID selected from the second group of IDs. When one unit is determined to be a master, it begins a process of selecting the first ID from the first group and communicating it to the slave units.